This invention relates to an internal cooling circuit for a stage two bucket in a gas turbine.
High gas path temperatures are required to achieve high output and high efficiency in gas turbine machines. Several rows (or stages) of rotating blades or buckets, made from various high temperature alloys, are used in the gas turbine to extract energy from the hot gas path. To maintain temperatures of the first and second stage buckets within the material design limits, internal cooling is required. For the high gas path temperatures expected in advanced gas turbine engines, cooling air is not attractive due to the high cycle efficiency penalties associated with using compressor discharge air. Steam is attractive as a viable alternative cooling medium due to its high heat capacity and its availability in a combined cycle unit which includes both steam and gas turbines. This invention addresses the design of an internal cooling circuit for a closed circuit, steam cooled, stage two bucket in a gas turbine engine.